The term microimagery in the context of the present application means information produced on photoconductive microfilm, aperture cards, microfiche and the like, as is well known in the art. Such information is typically reproduced on such photoconductive recording members or film by the steps of electrostatically charging the photoconductive film, exposing it to a light pattern corresponding to the information to be reproduced, toning with a liquid toner, drying, and fusing the image deposits directly onto the photoconductive film or transferring such deposits electrostatically or by other means such as heat and/or pressure. Such processes and apparatus to carry out the processes and related liquid toner applicators are described, for example, in U.S. Pat. Nos. 3,697,176, 2,820,890, 3,972,610, 4,176,940, 4,563,080 and 4,591,543.
Photoconductor films which are particularly suitable for use in microimagery processes for the reproduction or acquisition as well as retrieval of information are, for example, crystalline cadmium sulfide sputtered on a conductive layer contained on a transparent polyester substrate as disclosed in U.S. Pat. Nos. 4,025,339 and 4,269,919, and organic photoconductors coated over a conductive layer contained on a polyester or other transparent substrate.
In a typical microfiche acquisition system, the photoconductive fiche or card contains fractional image areas or so-called "frames", which are arranged in rows. The cards may be stored in a magazine. By automatic programming and indexing of all process steps, the required fiche may be called up to exit from the magazine and the selected frame thereon to be then processed for image acquisition or annotation. In certain types of apparatus the selected frame is stationary in the processing position, in which case the devices for all functions such as charging, exposure, toning, drying and fusing or transfer are caused to sequentially operate in such a processing position. In other instances, only some of such functions are performed in the processing positions, while for certain other functions, the selected frame is caused to move or pass by other functional devices which are stationary.
In all instances, however, only one frame is processed at one time and the image produced thereon must be fully dried and fused before the next frame can be processed. Thus, it is essential that the toner applicator applies liquid toner with a minimal quantity of carrier liquid and only to a fractional area of the fiche corresponding exactly to the area of a frame, and that after completion of toning, there are means provided to remove as much as possible excess toner or carrier liquid from the frame to allow rapid drying preparatory to fusing. It also is essential that such liquid toner or carrier liquid does not spread beyond the frame area and does not soil adjacent areas on the fiche.
Various methods have been proposed to limit the quantity of liquid toner applied to a frame and to purge excess liquid for rapid drying. Examples of such methods are disclosed, for instance, in U.S. Pat. Nos. 4,563,080 and 4,591,543. The methods disclosed in these patents, however, are inadequate to remove excess liquid toner or carrier liquid fast enough in very high speed systems where the total time available to perform all process functions per frame is one second or less.
It would therefore be advantageous to provide a method and means for applying liquid toner to fractional areas of a photoconductive recording member in processes involving microimagery where the liquid is applied only to the fractional areas without spreading to adjacent areas and excess liquid is removed from the fractional areas to enable rapid drying in a very high speed system. Another desirable advantage would be to tone a fractional area on a photoconductor to a predetermined image density.